The invention relates to pipes having integral bells, and more particularly to methods for manufacturing bells on filament wound pipes.
U.S. Pat. No. 3,499,815 discloses a method for manufacturing a filament wound pipe. This patent does not disclose a method for manufacturing a bell on such a pipe. It is known, however, as illustrated schematically in FIG. 1 of the drawings, to manufacture an integral bell on such a pipe by using a mandrel with a tapered or frustoconical outer surface portion that causes the pipe wall to have a corresponding flared or diverging end portion forming an integral bell. The bell portion is reinforced by winding additional layers of filament around the mandrel in the area of the bell portion. More particularly, a pipe 2 is formed by winding a plurality of layers 4 of filament bundles around a mandrel 6 having a frustoconical surface portion 8 that forms the bell portion of the pipe 2. Several additional layers 4 of filament bundles are wound around the bell portion to provide necessary reinforcement of the pipe wall to bell transition area.